Direct selective laser trabeculoplasty

ABSTRACT

A system (20) includes a radiation source (48) and a controller (44), configured to display a live sequence of images of an eye (25) of a patient (22), while displaying the sequence of images, cause the radiation source to irradiate the eye with one or more aiming beams (84), which are visible in the images, subsequently to causing the radiation source to irradiate the eye with the aiming beams, receive a confirmation input from a user, and in response to receiving the confirmation input, treat the eye by causing the radiation source to irradiate respective target regions of the eye with a plurality of treatment beams. Other embodiments are also described.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of (i) U.S. Provisional Appl.No. 62/692,868, entitled “Direct laser selective trabeculoplasty Process(DSLT) and Safeties,” filed Jul. 2, 2018, (ii) U.S. Provisional Appl.No. 62/739,238, entitled “Eye tracking flash illumination,” filed Sep.30, 2018, and (iii) U.S. Provisional Appl. No. 62/748,461, entitled“Crossed ranging beams,” filed Oct. 21, 2018. The respective disclosureof each of the aforementioned references is incorporated herein byreference.

FIELD OF THE INVENTION

The present invention relates to ophthalmological devices and methodsfor the treatment of glaucoma, ocular hypertension (OHT), and otherdiseases.

BACKGROUND

In a trabeculoplasty procedure, a radiation source irradiates thetrabecular meshwork in an eye of a patient with one or more treatmentbeams, thus lowering the intraocular pressure in the eye.

Geffen, Noa, et al., “Transscleral selective laser trabeculoplastywithout a gonioscopy lens,” Journal of glaucoma 26.3 (2017): 201-207describes a study to investigate results of selective lasertrabeculoplasty (SLT) performed directly on the sclera without agonioscopy lens.

US Patent Application Publication 2015/0366706 to Belkin, whosedisclosure is incorporated herein by reference, describes an apparatusincluding a probe and a processor. The probe is positioned adjacent toan eye of a patient and is configured to irradiate a trabecular meshworkof the eye with one or more optical beams. The processor is configuredto select one or more target regions of the trabecular meshwork, and tocontrol the probe to irradiate the selected target regions with theoptical beams.

SUMMARY OF THE INVENTION

There is provided, in accordance with some embodiments of the presentinvention, a system including a radiation source and a controller. Thecontroller is configured to display a live sequence of images of an eyeof a patient, and, while displaying the sequence of images, cause theradiation source to irradiate the eye with one or more aiming beams,which are visible in the images. The controller is further configuredto, subsequently to causing the radiation source to irradiate the eyewith the aiming beams, receive a confirmation input from a user, and, inresponse to receiving the confirmation input, treat the eye by causingthe radiation source to irradiate respective target regions of the eyewith a plurality of treatment beams.

In some embodiments, the system further includes:

a focusing lens; and

one or more beam-directing elements,

and the controller is configured to cause the radiation source toirradiate the eye with the treatment beams by firing the treatment beamsat the beam-directing elements through the focusing lens, such that thebeams are focused by the focusing lens prior to being directed, by thebeam-directing elements, toward the respective target regions.

In some embodiments, the aiming beams impinge on at least part of eachof the target regions.

In some embodiments, the controller is further configured tosuperimpose, on each of the images, a marker passing through each of thetarget regions.

In some embodiments, the marker is elliptical.

In some embodiments, at least part of each of the target regions islocated within 1 mm of a limbus of the eye.

In some embodiments, the controller is further configured to:

superimpose a marker on each of the images, and

prior to treating the eye, by processing the images, verify respectivepositions of the aiming beams with respect to the marker,

and the controller is configured to treat the eye in response toverifying the positions of the aiming beams.

In some embodiments, the controller is configured to verify thepositions of the aiming beams by verifying that the aiming beams overlapthe marker.

In some embodiments, the controller is configured to verify thepositions of the aiming beams by verifying that the aiming beams lieoutside the marker.

In some embodiments, the controller is configured to treat the eye suchthat respective edges of the treatment beams impinge on respectiveportions of the eye over which the marker is superimposed.

In some embodiments, the marker is elliptical.

In some embodiments, the controller is further configured to:

prior to displaying the live images, display a still image of the eye,

identify an elliptical portion of the eye in the still image, based oninput from the user, and

in response to identifying the elliptical portion of the eye,superimpose an elliptical marker over the elliptical portion of the eyein each of the images.

In some embodiments, the controller is configured to superimpose theelliptical marker over the elliptical portion of the eye by:

subsequently to identifying the elliptical portion of the eye,identifying an offset from a center of a limbus of the eye to a centerof the elliptical portion in the still image, and

for each image of the images:

-   -   identifying the center of the limbus in the image, and    -   superimposing the elliptical marker on the image such that the        center of the elliptical marker is at the identified offset from        the center of the limbus.

In some embodiments, the controller is configured to identify theelliptical portion of the eye by:

displaying, over the still image, (i) the elliptical marker, and (ii) arectangle circumscribing the elliptical marker, and

subsequently to displaying the elliptical marker and the rectangle, inresponse to the user adjusting the rectangle, adjusting the ellipticalmarker such that the elliptical marker remains circumscribed by therectangle, until the elliptical marker is superimposed over the portionof the eye.

In some embodiments, the controller is further configured to identify alimbus of the eye in the still image, and the controller is configuredto display the elliptical marker over the limbus.

In some embodiments, the system further includes a camera configured to:

acquire the images, and

acquire a still image of the eye, prior to acquiring the images,

and the controller is further configured to:

-   -   based on the still image of the eye, identify a static region in        a field of view of the camera that includes a pupil of the eye,        and    -   treat the eye such that each of the treatment beams impinges on        the eye outside the static region.

In some embodiments, the system further includes one or morebeam-directing elements,

the controller is configured to treat the eye by aiming thebeam-directing elements at the target regions in sequence and firing thetreatment beams at the beam-directing elements, and

the controller is further configured to inhibit the beam-directingelements from being aimed at the static region even while none of thetreatment beams is being fired.

In some embodiments, the controller is configured to identify the staticregion by:

receiving, from the user, a limbus-locating input indicating a locationof the limbus in the still image, and

identifying the static region based on the location of the limbus.

In some embodiments,

the images are first images and the aiming beams are first aiming beams,

the system further includes a camera configured to acquire multiplesecond images of the eye while treating the eye, and

the controller is configured to treat the eye by iteratively:

-   -   verifying a position of a respective second aiming beam in the        second image, and    -   in response to the verifying, firing a respective one of the        treatment beams at the eye.

In some embodiments, the controller is configured to verify the positionby verifying that a distance between the second aiming beam and arespective one of the target regions is less than a predefinedthreshold.

In some embodiments, the controller is configured to fire the respectiveone of the treatment beams at the respective one of the target regions.

In some embodiments, the system further includes an illumination source,and the controller is further configured to cause the illuminationsource to intermittently flash visible light at the eye such that thelight illuminates the eye at least during respective acquisitions of thesecond images.

In some embodiments, a peak average intensity of the light over aduration of each of the flashes is between 0.003 and 3 mW/cm².

In some embodiments, the controller is configured to cause theillumination source to flash the light at a frequency of at least 60 Hz.

In some embodiments, the frequency is at least 100 Hz.

In some embodiments, the system further includes an illumination source,and the controller is further configured to cause the illuminationsource to illuminate the eye with near-infrared light at least duringrespective acquisitions of the second images.

In some embodiments, the controller is further configured to cause theillumination source to intermittently flash visible light at the eyewhile treating the eye.

In some embodiments, the system further includes an optical unitincluding the radiation source and a plurality of beam emitters,

and the controller is further configured to, prior to causing theradiation source to irradiate the eye with the aiming beams, cause thebeam emitters to shine a plurality of range-finding beams on the eye,the range-finding beams being shaped to define different respectiveportions of a predefined composite pattern such that the predefinedcomposite pattern is formed on the eye only when the optical unit is ata predefined distance from the eye.

In some embodiments, the range-finding beams are shaped to define twoperpendicular shapes, and the predefined composite pattern includes across.

In some embodiments, the system further includes an optical unitincluding the radiation source, and the controller is configured tocause the radiation source to irradiate the target regions while theoptical unit is directed obliquely upward toward the eye and the eyegazes obliquely downward toward the optical unit.

In some embodiments, the system further includes a wedge, and theoptical unit is directed obliquely upward toward the eye by virtue ofbeing mounted on the wedge.

There is further provided, in accordance with some embodiments of thepresent invention, a system, including a wedge, an optical unit mountedon the wedge such that the optical unit is directed obliquely upward,the optical unit including a radiation source, and a controller. Thecontroller is configured to treat an eye of a patient by causing theradiation source to irradiate respective target regions of the eye witha plurality of treatment beams while the eye gazes obliquely downwardtoward the optical unit.

There is further provided, in accordance with some embodiments of thepresent invention, a method including displaying a live sequence ofimages of an eye of a patient. The method further includes, whiledisplaying the sequence of images, irradiating the eye with one or moreaiming beams, which are visible in the images. The method furtherincludes, subsequently to irradiating the eye with the aiming beams,receiving a confirmation input from a user, and in response to receivingthe confirmation input, treating the eye by irradiating respectivetarget regions of the eye with a plurality of treatment beams.

The present invention will be more fully understood from the followingdetailed description of embodiments thereof, taken together with thedrawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a system for performing atrabeculoplasty, in accordance with some embodiments of the presentinvention;

FIG. 2 is a schematic illustration of trabeculoplasty device, inaccordance with some embodiments of the present invention;

FIG. 3 is a schematic illustration of a pre-treatment procedure, inaccordance with some embodiments of the present invention; and

FIG. 4 is a schematic illustration of an example algorithm forperforming an automated trabeculoplasty procedure, in accordance withsome embodiments of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS Overview

Embodiments of the present invention provide an automatedtrabeculoplasty device configured to perform a trabeculoplasty procedureon an eye safely and efficiently. The trabeculoplasty device comprises acontroller and an optical unit, which comprises a radiation source, acamera, and beam-directing elements. As described in detail below, thecontroller is configured to control the radiation source and thebeam-directing elements in response to feedback from the camera, suchthat the beam-directing elements direct beams of radiation, which areemitted by the radiation source, toward the appropriate locations on theeye. The emitted beams of radiation include both treatment beams, whichirradiate the trabecular meshwork of the eye, and aiming beams, whichare used to help aim the treatment beams.

Typically, prior to the procedure, the controller displays a live videoof the eye in which two ellipses are superimposed over the eye: an innerellipse, which marks the limbus of the eye, and an outer ellipse,displaced from the inner ellipse by a small distance, which passesthrough or near each of the target regions that are to be irradiated bythe treatment beams. The controller further simulates the procedure bysweeping an aiming beam over the outer ellipse, typically such that theaiming beam impinges on at least part of each target region.Advantageously, this simulation may help the physician visualize thepath along the eye that is to be targeted by the treatment beams, i.e.,the path along which the target regions lie. After the physicianconfirms the targeted path along the eye, the controller causes theradiation source to fire the treatment beams at the target regions.

It is noted that since each beam of radiation generally impinges on theeye with a non-infinitesimal spot size, the present applicationgenerally describes each beam as impinging on a “region” of the eye,whose area is a function of the spot size, rather than impinging at a“point” on the eye. Thus, for example, the present application refers to“target regions,” rather than “target points.” Nonetheless, in thecontext of the present application, including the claims, references tocalculating the location of a target region may refer to implicitlycalculating the location of the region by calculating the location of asingle point within the region, such as the point at the center or edgeof the region at which the center or edge (respectively) of the beam isto be aimed. (Even if, subsequently, the center or edge of the beamdeviates slightly from the calculated point, the present application,including the claims, may consider the beam to have impinged on thecalculated target region.)

Typically, prior to simulating the procedure as described above, thecontroller acquires a still image of the eye, and identifies the limbusin the still image. The controller then superimposes the aforementionedinner ellipse over the limbus. Subsequently, the controller allows thephysician to modify the position and/or shape of the inner ellipse, suchthat the inner ellipse marks the limbus per the physician's definitionthereof. (Since the limbus is generally not well defined, the locationof the limbus per the physician may differ slightly from the locationautomatically identified by the controller.) For example, the controllermay circumscribe the inner ellipse by a rectangle, and then allow thephysician to adjust the ellipse by dragging the sides or corners of thecircumscribing rectangle.

As the present inventors have observed, the trabecular meshwork may beirradiated most effectively when the treatment beams impinge on the eyeat or near the limbus, which may be identified by the user as describedabove or automatically identified by the controller. Hence, in someembodiments of the present invention, the controller causes theradiation source to target the limbus or a portion of the eye near thelimbus. For example, at least part of each target region may be locatedwithin 1 mm (e.g., within 400 microns) of the limbus. As a specificexample of the above, the center of each target region may be locatedwithin 1 mm (e.g., within 400 microns) of the limbus, such that thecenter of each treatment beam impinges on the eye within 1 mm (e.g.,within 400 microns) of the limbus.

During both the simulated treatment and the actual treatment, the cameraacquires images of the eye at a relatively high frequency (e.g., at afrequency greater than 40 Hz or 50 Hz), and the controller tracks motionof the eye by identifying the center of the limbus in each of theacquired images. In response to identifying the center of the limbus,during the simulated treatment, the controller may move the inner andouter ellipses such that the inner ellipse remains positioned over thelimbus as defined by the physician, and the outer ellipse remains at aconstant distance from the inner ellipse, even as the eye moves.Similarly, during the procedure, the controller may calculate the centeror edge of each target region by adding the appropriate (x, y) offset tothe identified limbus center. Advantageously, due to this feedbackprocess, the safety and efficacy of the procedure is greatly improved.

Moreover, as an additional safety measure, the controller may define aregion, referred to herein as a “forbidden zone.” in the aforementionedstill image. The forbidden zone encompasses the pupil of the eye, alongwith, typically, a portion of the eye surrounding the pupil. Theforbidden zone is static, in that it is defined in terms of the field ofview (FOV) of the camera, and is not adjusted even in response todetected motion of the eye. The controller may then prevent any of thetreatment beams from striking the forbidden zone. Moreover, thecontroller may prevent the beam-directing elements from being aimed atthe forbidden zone, even while the radiation source is inactive. Thus,the retina of the eye is protected from any potential (though unlikely)stray beams.

In some embodiments, the trabeculoplasty device further comprises avisible light source, and the controller is configured to cause thevisible light source to flash visible light at the eye such that thevisible light is on at least while each image is acquired.Advantageously, the flash of light reduces the time needed to acquirethe image, such that the position of the target region calculatedresponsively to the image does not move significantly before the aimingbeam or treatment beam is fired at the target region. Moreover, theflash may constrict the pupil of the eye, thus further protecting theretina from any potential stray beams.

Typically, the light is flashed at a sufficiently high frequency, and/oreach pulse of light has a sufficiently long duration, such that theflashing is unnoticeable to the patient. Nonetheless, the total energyof the flashed light is low enough such that the light does not damagethe retina.

Alternatively, to reduce the time required for image acquisition withoutdiscomforting the patient, the eye may be illuminated with near-infraredlight. In addition, optionally, visible light may be flashed at the eye,such that the visible light is on while the images are acquired and/orbetween image acquisitions.

Embodiments of the present invention further provide a technique tofacilitate positioning the trabeculoplasty device at the correctdistance (or “range”) from the eye. Conventionally, this type ofpositioning is performed by aiming two circular range-finding beams atthe eye from the device, and moving the device toward or away from theeye until the two beams overlap. However, as the present inventors haveobserved, for several reasons, it may be difficult to use this techniquefor positioning the trabeculoplasty device; for example, the sclera iscovered by a conjunctiva that may distort and reflect the range-findingbeams, thus making it difficult to discern that the beams overlap.Hence, in embodiments of the present invention, the range-finding beamsare given different respective shapes, such that the beams form aparticular pattern only when the trabeculoplasty device is positioned atthe correct distance from the eye. For example, the range-finding beamsmay be shaped as perpendicular ellipses, such that the range-findingbeams form a cross over the eye only at the correct range.

In some embodiments, to reduce obstruction of the sclera by the uppereyelid, the optical unit of the trabeculoplasty device is mounted on awedge, such that the camera and radiation source are directed obliquelyupward. The patient's gaze is then directed, obliquely downward, towardthe optical unit, such that the upper portion of the patient's sclera isexposed.

Although the present description relates mainly to a trabeculoplastyprocedure, the techniques described herein may also be applied toautomatic photocoagulation procedures, iridotomy procedures,capsulectomy procedures, lens removals, or any other relevantophthalmological procedures. The target of the radiation may include thetrabecular meshwork and/or any other suitable portion of the eye, suchas the endothelial stem cells or Schlemm's canal cells of the eye.Embodiments of the present invention may be used to treat glaucoma,ocular hypertension (OHT), and other diseases.

System Description

Reference is initially made to FIG. 1, which is a schematic illustrationof a system 20, comprising a trabeculoplasty device 21, for performing atrabeculoplasty, in accordance with some embodiments of the presentinvention. Reference is further made to FIG. 2, which is a schematicillustration of trabeculoplasty device 21, in accordance with someembodiments of the present invention.

Trabeculoplasty device 21 comprises an optical unit 30. Optical unit 30comprises a radiation source 48, which is configured to irradiate an eye25 of a patient 22 with both aiming beams and treatment beams asdescribed herein. Optical unit 30 further comprises one or morebeam-directing elements, comprising, for example, one or more galvomirrors 50 (which may be referred to collectively as a “galvo scanner”)and/or a beam combiner 56. Before the firing of each beam 52 fromradiation source 48, or while the beam is being emitted, a controller 44aims the beam-directing elements at the desired target region on eye 25such that the beam is directed, by the beam-directing elements, towardthe target region. For example, the beam may be deflected by galvomirrors 50 toward beam combiner 56, which may then deflect the beamthrough an aperture 58 at the front of the optical unit such that thebeam impinges on the target region. Each beam emitted by the radiationsource may have an elliptical (e.g., circular) shape, a square shape, orany other suitable shape.

Typically, the radiation source comprises two lasers: one for firingaiming beams as described herein, and another for firing treatment beamsas described herein. As a purely illustrative example, the treatmentlaser may comprise an Ekspla™ NL204-0.5K-SH laser (modified, forexample, to include an attenuator, energy meter, and mechanicalshutter), while the aiming laser may comprise a Laser Components™FP-D-635-1DI-C-F laser. Typically, both the aiming beams and thetreatment beams comprise visible light.

Alternatively or additionally to a laser, the radiation source maycomprise any other suitable emitter configured to emit radiationbelonging to any suitable portion of the electromagnetic spectrum,including, for example, microwave radiation, infrared radiation, X-rayradiation, gamma radiation, or ultraviolet radiation.

In some embodiments, each beam 52 passes through a beam expander (notshown), which expands and then re-collimates the beam, prior to reachingthe galvo scanner. In such embodiments, optical unit 30 typicallycomprises an F-theta lens 51, configured to focus each beam subsequentlyto the direction of the beam by the galvo scanner.

In other embodiments, a focusing lens is disposed between the radiationsource and the galvo scanner; for example, the aforementioned beamexpander may comprise a focusing lens instead of a collimating lens, orthe optical unit may comprise a focusing lens in addition to the beamexpander. In such embodiments, each of the beams is focused by thefocusing lens prior to being directed by the beam-directing elements,such that F-theta lens 51 may not be needed.

Optical unit 30 further comprises a camera 54. Before and during theprocedure, camera 54 acquires multiple images of the patient's eye,typically at a relatively high frequency. Controller 44 processes theseimages and, in response thereto, controls radiation source 48 and thebeam-directing elements, as described below with reference to FIGS. 3-4.As shown in FIG. 2, camera 54 may be positioned behind beam combiner 56,such that the camera receives light via the beam combiner.

Typically, optical unit 30 further comprises an illumination source 60comprising, for example, one or more light emitting diodes (LEDs), suchas a ring of LEDs surrounding aperture 58. In such embodiments,controller 44 may cause illumination source 60 to intermittently flashlight at the eye, as further described below with reference to FIG. 4.(For ease of illustration, the connection between controller 44 andillumination source 60 is not shown explicitly in FIG. 2.)

Optical unit 30 is mounted onto an XYZ stage 32, which is controlled bya control mechanism 36, such as a joystick. Using control mechanism 36,a user of system 20, such as an ophthalmological surgeon or anotherphysician, may position the optical unit at the appropriate positionprior to treating the eye of the patient. In some embodiments, XYZ stage32 comprises locking elements configured to inhibit motion of the stagefollowing the positioning of the stage.

In some embodiments, XYZ stage 32 comprises one or more motors, andcontrol mechanism 36 is connected to interface circuitry 46. As the usermanipulates the control mechanism, interface circuitry 46 translatesthis activity into appropriate electronic signals, and outputs thesesignals to controller 44. In response to the signals, the controllercontrols the motors of the XYZ stage. In other embodiments, XYZ stage 32is controlled manually by manipulating the control mechanism.

Typically, before the radiation source fires any beams at the eye, theuser, using control mechanism 36, positions the optical unit at apredefined distance D from the eye. To facilitate this positioning, theoptical unit may comprise a plurality of beam emitters 62 (comprising,for example, respective laser diodes), which are configured to shine aplurality of range-finding beams 64 on the eye, e.g., such that theangle between the beams is between 30 and 100 degrees. As furtherdescribed below with reference to FIG. 3, range-finding beams 64 areshaped to define different respective portions of a predefined compositepattern, such that the predefined composite pattern is formed on the eyeonly when the optical unit is at the predefined distance from the eye.Hence, in response to observing the composite pattern, the user mayascertain that the optical unit is at the predefined distance.

System 20 further comprises a headrest 24, which is mounted onto ahorizontal surface 38, such as a tray or table top. Headrest 24comprises a forehead rest 26 and a chinrest 28. During thetrabeculoplasty procedure, patient 22 presses his forehead againstforehead rest 26 while resting his chin on chinrest 28.

In some embodiments, headrest 24 further comprises an immobilizationstrap 27, configured to secure the patient's head from behind and thuskeep the patient's head pressed against the headrest. Immobilizationstrap 27 may comprise a single segment extending from the headrest atone side of the head and configured to fasten to the headrest at theother side of the head, or two segments that extend from the headrest atopposite sides of the head and are configured to fasten to one anotherbehind the head. Optionally, the immobilization strap may comprise asensor configured to detect when the immobilization strap is properlyfastened. For example, fastening the immobilization strap may cause anelectrical circuit to be closed, and the sensor may then detect the flowof electric current through the circuit and generate an output (e.g., bylighting an LED) responsively thereto.

In some embodiments, headrest 24 further comprises one or more sensors,which may be disposed, for example, on the forehead rest or chinrest.Each of these sensors may be configured to generate an output indicatingwhether the patient's head is resting on the headrest as required.Examples of suitable sensors include capacitive, resistive, andpiezoelectric sensors. Alternatively or additionally, the headrest maycomprise one or more switches or force-sensitive resistors, such as theSparkfun™ 9375.

In some embodiments, to contain any radiation reflected by the eye, aphysical block is placed around the eye. For example, a hood may beplaced over the chinrest and/or over the patient's head. Alternativelyor additionally, a hood may be coupled to the face of device 21.

In some embodiments, device 21 further comprises a base unit 34, whichis mounted onto surface 38, and XYZ stage 32 is mounted onto base unit34. In such embodiments, controller 44 and interface circuitry 46 may bedisposed within the base unit. In other embodiments, the XYZ stage ismounted directly onto surface 38.

Typically, as shown in FIG. 1, while irradiating the patient's eye, theoptical unit is directed obliquely upward toward the eye while the eyegazes obliquely downward toward the optical unit, i.e., the optical path23 between the eye and the optical unit is oblique, rather thanhorizontal. For example, optical path 23 may be oriented at an angle θof between five and twenty degrees. Advantageously, this orientationreduces occlusion of the patient's eye by the patient's upper eyelid andassociated anatomy. Optionally, for additional exposure of the eye, afinger, a speculum, or another tool may be used to retract one or bothof the eyelids.

In some embodiments, as shown in FIG. 1, the oblique orientation of theoptical path is achieved by virtue of the optical unit being mounted ona wedge 40, which is mounted on the XYZ stage. In other words, theoptical unit is mounted onto the XYZ stage via wedge 40.

Alternatively or additionally to using wedge 40, the oblique orientationof the optical path may be achieved by tilting the patient's headbackward. For example, forehead rest 26 and/or chinrest 28 may comprisean adjustable-length strap, and the patient's head may be tiltedbackward by adjusting the length of the strap. (For example, theforehead strap may be constricted.) To facilitate this adjustment, theadjustable-length strap may comprise a worm-type drive, a hook-and-loopfastener, snaps, locking pins, knots, and/or any other suitablemechanism.

In other embodiments, the patient's head is tilted slightly forward,e.g., by angling headrest 24 (or at least chinrest 28) toward theoptical unit, such that the patient's head rests more securely on theheadrest.

System 20 further comprises a monitor 42, configured to display theimages of the eye acquired by the camera, as described in detail belowwith reference to FIG. 3. Monitor 42 may be disposed at any suitablelocation, such as on surface 38 next to device 21. In some embodiments,monitor 42 comprises a touch screen, and the user inputs commands to thesystem via the touch screen. Alternatively or additionally, system 20may comprise any other suitable input devices, such as a keyboard or amouse, which may be used by the user.

In some embodiments, monitor 42 is connected directly to controller 44over a wired or wireless communication interface. In other embodiments,monitor 42 is connected to controller 44 via an external processor, suchas a processor belonging to a standard desktop computer.

It is emphasized that the configuration shown in FIG. 2 is provided byway of example only. Moreover, alternatively or additionally to thecomponents shown in FIG. 2, device 21 may comprise any suitablecomponents. For example, the device may comprise an additionalillumination source, such as an LED, on which the patient may fixateduring the procedure. Such an illumination source may be disposed, forexample, near aperture 58 or next to the camera.

In some embodiments, at least some of the functionality of controller44, as described herein, is implemented in hardware, e.g., using one ormore Application-Specific Integrated Circuits (ASICs) orField-Programmable Gate Arrays (FPGAs). Alternatively or additionally,controller 44 may perform at least some of the functionality describedherein by executing software and/or firmware code. For example,controller 44 may comprise a central processing unit (CPU) and randomaccess memory (RAM). Program code, including software programs, and/ordata may be loaded into the RAM for execution and processing by the CPU.The program code and/or data may be downloaded to the controller inelectronic form, over a network, for example. Alternatively oradditionally, the program code and/or data may be provided and/or storedon non-transitory tangible media, such as magnetic, optical, orelectronic memory. Such program code and/or data, when provided to thecontroller, produce a machine or special-purpose computer, configured toperform the tasks described herein.

In some embodiments, the controller comprises a system on module (SOM),such as the Varisite™ DART-MX8M.

In some embodiments, controller 44 is disposed externally to device 21.Alternatively or additionally, the controller may cooperatively performat least some of the functionality described herein with another,external processor.

The Pre-Treatment Procedure

Reference is now made to FIG. 3, which is a schematic illustration of apre-treatment procedure, in accordance with some embodiments of thepresent invention.

By way of introduction, the procedure illustrated in FIG. 3 includesthree steps, referred to in the figure as steps A-C. For each of thesesteps, FIG. 3 shows an image of eye 25, which is acquired by camera 54(FIG. 2) and displayed, by controller 44 (FIG. 2), on monitor 42.Typically, a graphic user interface (GUI) 68 is further displayed onmonitor 42 beside each image. GUI 68 may include text boxes containingrelevant alphanumeric data and/or instructions for the user, buttons forconfirming or rejecting a particular treatment plan, and/or any otherrelevant widgets.

In step A, the user positions optical unit 30 (FIG. 2) such that thecenter of the eye is approximately at the center of the FOV of thecamera. The user also positions the optical unit at the correct distancefrom the eye, such that the treatment beams have the proper spot size onthe eye. As described above with reference to FIG. 2, this positioningis typically facilitated by range-finding beams 64, which are shaped todefine different respective portions of a predefined composite pattern66 such that pattern 66 is formed on the eye only when the optical unitis at the correct distance. Typically, the user forms the compositepattern on the sclera of the eye, near the limbus. (Typically, while theposition of the optical unit is adjusted, the controller displays a livesequence of images of the patient's eye.)

For example, as shown in FIG. 3, the range-finding beams may be shapedto define two perpendicular shapes, such as two perpendicular ellipses,rectangles, or lines, which form a cross on the eye only when theoptical unit is at the correct distance. Alternatively, therange-finding beams may be shaped to define two arcs or semicircles,which form a circle, or two triangles or arrowheads, which form adiamond or X shape. Any suitable optical elements such as diffractiveoptical elements (DOEs), holograms, or axicons may be used to facilitategenerating these patterns.

In other embodiments, only a single range-finding beam is emitted, and acomputer-generated pattern is superimposed over the images of the eye.When the optical unit is at the correct distance, the range-finding beamand the computer-generated pattern overlap or form composite pattern 66.

In response to observing pattern 66, the user indicates to thecontroller that the optical unit is at the correct distance from theeye. For example, the user may click an appropriate button on GUI 68. Inresponse to this input, the controller proceeds to step B of thepre-treatment procedure.

In step B, the controller displays a still image 71 of the eye.Subsequently, based on input from the user, the controller identifies anelliptical (e.g., circular or almost circular) portion of the eye, suchas the limbus 69 of the eye. For example, the controller may identifythe portion of the eye in response to the user superimposing anelliptical marker 78 over the portion of the eye. The position of marker78 may then be used to compute the respective positions of thetreatment-beam target regions, as further described below.

For example, the controller may display, over the still image, bothmarker 78 and a rectangle 80 circumscribing (or “bounding”) the marker.Subsequently, the user may adjust rectangle 80, e.g., by dragging thesides or corners of the rectangle using a mouse or touch screen. (Insome embodiments, the system allows the user to toggle between a roughand fine adjustment of the rectangle.) In response to the user adjustingthe rectangle, the controller may adjust marker 78 such that the markerremains circumscribed by the rectangle, until the marker is superimposedover the limbus as defined by the user (or over another portion of theeye). Subsequently, the user may indicate to the controller (e.g., viaGUI 68) that the marker is superimposed over the limbus as defined bythe user.

In some embodiments, the controller superimposes two horizontal linestangent to the top and bottom extremities of marker 78, respectively,and two vertical lines tangent to the left and right extremities ofmarker 78, respectively, without necessarily causing the lines tointersect each other and thus define a rectangle. In such embodiments,the user may adjust marker 78 by dragging the lines.

Typically, prior to allowing the user to adjust marker 78, thecontroller, using an edge-detection algorithm or any other suitableimage-processing technique, identifies the limbus in the still image andthen displays marker 78 over the limbus. (It is noted that thecontroller may approximate the form of the limbus by any suitable shape,such as an elliptical shape aligned with the vertical and horizontalaxes or rotated by any suitable angle.) Advantageously, by initializingthe placement of marker 78 in this manner, the time required to adjustthe marker is reduced. (Since the limbus is generally not a well-definedfeature, the location of the limbus as identified by the user typicallydiffers slightly from the location of the limbus as identified initiallyby the controller; hence, as presently described, the user is allowed toadjust the marker.)

Alternatively or additionally to adjusting the rectangle, the user maydirectly adjust marker 78 by inputting relevant parameters. For example,for an elliptical (e.g., circular) marker, the user may input thecoordinates of the center of the marker and one or two diameters of themarker. Alternatively or additionally, the user may adjust the marker byadjusting an input to the limbus-identification algorithm (such as athreshold for edge detection) that is executed by the controller. As yetanother option, the user may manipulate marker 78 directly.

In alternative embodiments, marker 78 is not shown at all. In suchembodiments, the user may indicate the position of the limbus bydragging the rectangle or lines that would bound the marker if themarker were shown. As yet another alternative, for greater precision, anon-elliptical marker having another shape that more preciselycorresponds to the shape of limbus 69 may be used instead of ellipticalmarker 78.

Typically, prior to the execution of the pre-treatment procedureillustrated in FIG. 3, the user (using GUI 68, or any other suitableinput interface) specifies the respective positions of a plurality oftarget regions relative to the portion of the eye that is to beidentified in step B. Alternatively, these parameters may be defined inadvance, prior to use of the system by the user.

For example, the user may specify an elliptical path of target regionsadjacent to the limbus, by specifying the number of target regions andthe distance from the limbus (or from the center thereof) at which thecenter or edge of each of the target regions is to be located.Alternatively, the user may specify one or more arced paths, byspecifying, in addition to the aforementioned parameters, (i) an angularspan of each arc, and (ii) the location of each arc. (For example, theuser may specify a 180 degree arc around the bottom or top half of thelimbus, or respective 90 degree arcs at the top and bottom.) Given thisinput, and given the location of the limbus as indicated by the user,the controller calculates the respective positions of the targetregions, typically relative to the center of the limbus as identified bythe controller. (In some embodiments, the controller calculates theposition of the ellipse or arc specified by the user, but does notcalculate the specific positions of the target regions on the ellipse orarc until after the performance of step C, described below.)

As a purely illustrative example, the user may specify that the centeror edge of each target region is to be at a distance of d1 from thelimbus as marked by the user, at a different respective angle θ_(i)relative to the center of the limbus. The user may then, during step B,adjust marker 78 such that the center of the marker is at (x0+Δx,y0+Δy), wherein (x0, y0) is the center of the limbus as identified bythe controller. In such a case, assuming that marker 78 is a circle withradius R, the controller may compute the offset from the limbus centerof the center or edge of each target region as (Δx+(R+d1)cos(θ_(i)),Δy+(R+d1)sin(θ_(i))). (It is noted that d1 may be zero, i.e., the centeror edge of each target region may coincide with the limbus as marked bythe user, such that the respective centers or edges (respectively) ofthe treatment beams impinge on the limbus as marked by the user.)Subsequently, during the procedure, as further described below withreference to FIG. 4, the controller may track the center of the limbusand, for each target region, compute the position of the region byadding this offset to the position of the center.

Typically, in step B, the controller also identifies, based on the stillimage, a static region 76 in the field of view (FOV) of the camera—alsoreferred to herein as a “forbidden zone”—that includes the pupil 74 ofthe eye, typically along with a “buffer” that includes a significantportion of the cornea 72 of the eye surrounding pupil 74. Typically, thesize of the buffer is set based on the maximum expected movement of theeye.

In some embodiments, region 76 is identified based on the location ofthe limbus as automatically identified by the controller or as marked bythe user. For example, the controller may identify region 76 as the setof all points in the FOV located inside the limbus at more than apredefined distance from the limbus. Alternatively, for example, thecontroller may identify the point at the center of the limbus or thecenter of the pupil, and then center region 76 at this center point. Insuch embodiments, region 76 may have any suitable shape, such as anelliptical or rectangular shape, and may have any suitable size. Thesignificance of region 76 is described below with reference to FIG. 4.(it is noted that region 76 is not necessarily displayed on monitor 42.)

Following step B, the controller proceeds to step C, in which thetrabeculoplasty procedure is simulated. In response to viewing thesimulation, the user may provide a confirmation input to the controller.e.g., by clicking an appropriate button (such as a “START” button) inGUI 68. This input confirms that the controller should proceed with theprocedure.

More specifically, in step C, the controller displays a live sequence ofimages (i.e., a live video) of the eye, and, while displaying thesequence of images, irradiates the eye with one or more aiming beams 84,which are visible in the images. Typically, the aiming beams are red;for example, each aiming beam may have a wavelength of between 620 and650 nm. In some embodiments, the color of the aiming beams is differentfrom that of the treatment beams; for example, whereas the aiming beamsmay be red, the treatment beams may be green, having a wavelength ofbetween 515 and 545 nm (e.g., 532 nm), for example.

While irradiating the eye with the aiming beams, the controller controlsthe beam-directing elements such that, if the treatment beams were to befired, the treatment beams would impinge on the calculated targetregions. Thus, the respective centers of the aiming beams may coincide,sequentially, with the center of each target region. Alternatively, ifF-theta lens 51 (FIG. 2) is used, and if the color of the aiming beamsis different from that of the treatment beams, chromatic aberrationintroduced by the F-theta lens may cause the aiming beams to be slightlyoffset from the target regions. Nevertheless, even in this case, theaiming beams typically impinge on at least part of each target region.

In some embodiments, the controller sweeps a single aiming beam alongthe eye, such that the aiming beam impinges on at least part of eachtarget region. In other embodiments, the controller fires a plurality ofaiming beams, such that each aiming beam impinges on at least part of adifferent respective one of the target regions.

Typically, while performing the simulation, the controller superimposesmarker 78 over the portion of the eye that was identified in step B. Tocompensate for any movement of the eye, the controller typicallyidentifies the center of the limbus in each of the images, and placesmarker 78 at the appropriate offset from the limbus. For example, if thefinal position of the center of marker 78 in the still image (step B) is(x0+Δx, y0+Δy), the controller may place marker 78 at an offset of (Δx,Δy) from the center of the limbus in each of the live images.

Alternatively or additionally to superimposing marker 78, the controllermay superimpose, on each of the images, another marker 82 passingthrough (e.g., through the center of) or near each target region. Theposition of marker 82 may be adjusted responsively to motion of the eye,by maintaining marker 82 at the proper offset from marker 78. Forexample, if the center of each target region is to be at a distance ofd1 from the limbus as marked by the user, marker 82 may be kept at adistance of d1 from marker 78. In some embodiments, marker 82 is adifferent color from that of marker 78.

Typically, while performing the simulation, the controller verifies thateach of the aiming beams was properly directed by the beam-directingelements. For example, the controller may process a feedback signal fromthe encoders for galvo mirrors 50. Alternatively or additionally, thecontroller, by processing the images, may verify the respectivepositions of the aiming beams with respect to marker 78, marker 82,and/or any other suitable marker superimposed on each of the images. Forexample, the controller may verify that each aiming beam (e.g., thecenter of each aiming beam) overlaps marker 82, and/or that the edge ofeach aiming beam touches marker 78. (In the context of the presentapplication, including the claims, the “edge” of a beam may be definedin terms of the knife-edge measure, the 1/e² width measure, the fullwidth at half maximum measure, or any other suitable measure.) Asanother example, the controller may verify that the center or edge ofeach aiming beam is positioned at the appropriate distance from marker78.

In response to verifying the positions of the aiming beams, thecontroller may proceed with the trabeculoplasty procedure, provided thatthe user provides the aforementioned confirmation input.

In some embodiments, if the user does not confirm the simulation, thetreatment is aborted. In other embodiments, the user may (e.g., via GUI68) adjust the path followed by the aiming beams. This adjustment may beperformed by returning to step B and adjusting marker 78, and/or byadjusting the distance from marker 78 at which each target region is tobe located. In such embodiments, the simulation may be repeated for eachnew path defined by the user, until the user confirms the path.

The Treatment Procedure

In response to receiving the aforementioned confirmation input from theuser, the controller treats the eye by irradiating the target regionswith respective treatment beams. The peak power of the treatment beamsis much higher than that of the aiming beams; furthermore, typically,the wavelength of the treatment beams is better suited for treating thetrabecular meshwork of the eye, relative to the wavelength of the aimingbeams.

More specifically, during the treatment, the controller continues tosweep an aiming beam through the target regions, or to fire respectiveaiming beams at the target regions, while acquiring images of the eye.As further described below with reference to FIG. 4, the controllerverifies the position of the aiming beam in each of the images, and inresponse thereto, fires a treatment beam at the eye. For example, thecontroller may fire the treatment beam at the target region on which theaiming beam impinged, or at the next target region.

Typically, the controller causes each of the treatment beams to impingeon the eye outside region 76 (FIG. 3), also referred to herein as a“forbidden zone.” (As noted above, region 76 is static, in that theregion is defined in terms of the FOV of the camera, and hence does notmove with the eye.) Moreover, as an extra precaution, the controller mayinhibit the beam-directing elements from being aimed at (i.e., from“traveling through”) region 76 even while none of the treatment beams isbeing fired. (Typically, the controller also applies these precautionarymeasures while firing the aiming beams during the pre-treatmentprocedure.)

Typically, while acquiring each of the images during the treatmentprocedure, the controller causes illumination source 60 (FIG. 2) toflash visible light (e.g., white light, red light, or green light) atthe eye. By virtue of this flashing, the required exposure time of thecamera may be reduced, e.g., by a factor of three or more; thus, forexample, the required exposure time may be reduced from 9 ms to 3 ms.Each flash may begin before, and/or end after, the acquisition of animage. Typically, the peak average intensity over the duration of eachflash is 0.003-3 mW/cm², which is generally high enough to reduce therequired camera exposure time and to constrict the pupil of the eyewithout causing harm to the patient.

Typically, the light is flashed at a frequency that is sufficiently highsuch that the patient does not notice the flashing, but rather,perceives steady illumination. For example, the light may be flashed ata frequency of at least 60 Hz, such as at least 100 Hz. (In suchembodiments, the duration of each flash (or “pulse”) is typically lessthan 3 ms, such as less than 2 ms or 1 ms.) Since the frequency of theflashing may be higher than the frame rate (i.e., the frequency at whichthe images are acquired), some of the flashes may occur between imageacquisitions. For example, the flashing frequency may be an integermultiple of the frequency at which images are acquired, such that theflashing is synchronized with the image acquisition. As a purelyillustrative example, with a frame rate of 60 Hz, the flashing frequencymay be 120 Hz or 180 Hz.

Alternatively, the light may be flashed at a lower frequency, but theduration of each flash may be increased such that steady illumination isperceived. For example, if the patient perceives flickering with aflashing frequency of 100 Hz and a 20% duty cycle, the duty cycle may beincreased to 40% by increasing the pulse width without changing thefrequency.

In some embodiments, illumination source 60 is configured to emitnear-infrared light. In such embodiments, near-infrared light may beshone continuously during the treatment, or at least while the imagesare acquired, in order to reduce the required camera exposure timewithout disturbing the patient. Optionally, illumination source 60 mayalso flash visible light at the eye during and/or between the imageacquisitions, so as to further reduce the required exposure time and/orto constrict the pupil.

Some further details regarding the trabeculoplasty procedure are nowprovided with reference to FIG. 4, which is a schematic illustration ofan example algorithm 86 for performing an automated trabeculoplastyprocedure, in accordance with some embodiments of the present invention.

To begin the procedure after approval of the simulated procedure by theuser, the controller, at an imaging-and-locating step 88, flashes lightat the eye, uses the camera to acquire an image of the eye during theflash, and locates the center of the limbus in the acquired image.Subsequently, at a target-calculating step 90, the controller calculatesthe position of the next target region, by adding the appropriate (x, y)offset to the location of the center of the limbus. After verifying thisposition, the target region is irradiated, as further described below.The controller then acquires another image, calculates the position ofthe next target region, verifies the position, and irradiates thetarget. In this manner, the controller iteratively irradiates the targetregions.

More specifically, for each calculated target region, the controllerchecks, at a first target-checking step 92, whether the target regionlies (even partly) in the forbidden zone, which, it will be recalled, isa static region in the FOV of the camera. (To perform this check, thecontroller does not necessarily explicitly calculate the boundaries ofthe target region; for example, the controller may check whether thepoint at the center of the target region lies more than a predefineddistance—equivalent to or slightly greater than the radius of the aimingbeam or treatment beam—from the border of the forbidden zone.) If not,the controller performs a second target-checking step 94, atwhich—provided that the target region was preceded by a previous targetregion—the controller checks whether the target region is at anacceptable distance from the previous target region. For example, thecontroller may check whether the distance between the target region andthe previous target region is less than a predefined threshold,indicating that the eye is relatively still. If the target region is notat an acceptable distance from the previous target region, or if thetarget region is in the forbidden zone, the controller returns toimaging-and-locating step 88.

If the calculated target region passes both first target-checking step92 and second target-checking step 94, the controller aims thebeam-directing elements at the target region, at an aiming step 96.Subsequently, the controller, at an aiming-beam-firing step 98, fires anaiming beam at the beam-directing elements, such that the aiming beam isdirected toward the target region by the beam-directing elements.Alternatively, a single aiming beam may be continuously emitted, suchthat there is no need to perform aiming-beam-firing step 98.

Subsequently, the controller performs imaging-and-locating step 88. Thecontroller then checks, at a limbus-center-checking step 100, whetherthe center of the limbus moved (relative to the most-recently acquiredimage) by more than a predefined threshold. If yes, the controllerreturns to target-calculating step 90, and recalculates the location ofthe target region with respect to the center of the limbus. Otherwise,the controller, at an aiming-beam-identifying step 102, identifies theaiming beam in the image.

Subsequently to identifying the aiming beam, the controller checks, at afirst aiming-beam-checking step 106, whether the aiming beam is in theforbidden zone. If the aiming beam is in the forbidden zone—indicatingrapid movement of the eye or a failure in the system—the controllerterminates the procedure. Otherwise, the controller checks, at a secondaiming-beam-checking step 108, whether the distance between the aimingbeam and the calculated target region is within a predefined threshold.If not, the controller returns to target-calculating step 90. Otherwise,the controller fires the treatment beam, at a treatment-beam-firing step110, such that the treatment beam impinges on the target region.

Typically, in addition to identifying and verifying the position of theaiming beam, the controller checks each image for any obstructions thatmay be obstructing the target region, including, for example, an eyelid,eyelashes, a finger, growths (such as pterygium), blood vessels, or aspeculum. In the event that an obstruction is identified, the targetregion may be shifted to avoid the obstruction. Alternatively, thetarget region may be skipped entirely, or the treatment procedure may beterminated.

In general, obstructions may be identified using any suitableimage-processing techniques, optionally in combination with input fromthe user. For example, prior to the treatment procedure, the user mayselect (e.g., with reference to the still image) one or more portions ofthe eye that constitute potential obstructions. Subsequently, thecontroller may use template matching, edge detection, or any othersuitable techniques—including, for example, identifying changes betweensuccessive images—to identify the selected portions of the eye. Suchtechniques may also be used to identify other static or dynamicobstructions that were not necessarily identified in advance by theuser. (It is noted that the definition of “obstruction” may vary betweenapplications; for example, whereas in some applications a particularblood vessel may constitute an obstruction, in other cases it may bedesired to irradiate the blood vessel.)

Following treatment-beam-firing step 110, the controller checks, at afinal checking step 112, whether all of the target regions have beentreated. If yes, the controller terminates the procedure. Otherwise, thecontroller returns to target-calculating step 90.

Advantageously, the time between the acquisition of each image and thefiring of the treatment beam is typically less than 15 ms, e.g., lessthan 10 ms. In some embodiments, this delay is reduced is even further,by firing the treatment beam between aiming step 96 andaiming-beam-firing step 98 (or, if a single aiming beam is continuouslyemitted, between aiming step 96 and imaging-and-locating step 88),instead of after second aiming-beam-checking step 108. (In suchembodiments, the aiming beam is used to verify post facto that thetreatment beam was fired correctly.)

In some embodiments, a separate routine executed by the controllermonitors the time from each image acquisition. If this time exceeds apredefined threshold (such as a threshold between 10 and 15 ms), thetreatment beam is not fired until after the next image is acquired andthe target position is recalculated.

It will be appreciated by persons skilled in the art that the presentinvention is not limited to what has been particularly shown anddescribed hereinabove. Rather, the scope of the present inventionincludes both combinations and subcombinations of the various featuresdescribed hereinabove, as well as variations and modifications thereofthat are not in the prior art, which would occur to persons skilled inthe art upon reading the foregoing description.

The invention claimed is:
 1. A system, comprising: a radiation source;one or more beam-directing elements; and a controller, configured to:display a live sequence of images of an eye of a patient, whiledisplaying the sequence of images, simulate an irradiation of one ormore target regions of the eye such that the simulated irradiation isvisible in the images, by directing the beam-directing elements at thetarget regions in sequence, verify the directing of the beam-directingelements by processing a feedback signal from an encoder for thebeam-directing elements, subsequently to simulating the irradiation,receive a confirmation input from a user, and in response to receivingthe confirmation input and to verifying the directing of thebeam-directing elements, treat the eye by causing the radiation sourceto irradiate the target regions of the eye with respective treatmentbeams.
 2. The system according to claim 1, further comprising a focusinglens, wherein the controller is configured to cause the radiation sourceto irradiate the eye with the treatment beams by firing the treatmentbeams at the beam-directing elements through the focusing lens, suchthat the beams are focused by the focusing lens prior to being directed,by the beam-directing elements, toward the target regions.
 3. The systemaccording to claim 1, wherein the controller is further configured tosuperimpose, on each of the images, a marker passing through each of thetarget regions.
 4. The system according to claim 3, wherein the markeris elliptical.
 5. The system according to claim 1, wherein at least partof each of the target regions is located within 1 mm of a limbus of theeye.
 6. The system according to claim 1, wherein the controller isfurther configured to: prior to displaying the live images, display astill image of the eye, identify an elliptical portion of the eye in thestill image, based on input from the user, and in response toidentifying the elliptical portion of the eye, superimpose an ellipticalmarker over the elliptical portion of the eye in each of the images. 7.The system according to claim 6, wherein the controller is configured tosuperimpose the elliptical marker over the elliptical portion of the eyeby: subsequently to identifying the elliptical portion of the eye,identifying an offset from a center of a limbus of the eye to a centerof the elliptical portion in the still image, and for each image of theimages: identifying the center of the limbus in the image, andsuperimposing the elliptical marker on the image such that the center ofthe elliptical marker is at the identified offset from the center of thelimbus.
 8. The system according to claim 6, wherein the controller isconfigured to identify the elliptical portion of the eye by: displaying,over the still image, (i) the elliptical marker, and (ii) a rectanglecircumscribing the elliptical marker, and subsequently to displaying theelliptical marker and the rectangle, in response to the user adjustingthe rectangle, adjusting the elliptical marker such that the ellipticalmarker remains circumscribed by the rectangle, until the ellipticalmarker is superimposed over the portion of the eye.
 9. The systemaccording to claim 8, wherein the controller is further configured toidentify a limbus of the eye in the still image, and wherein thecontroller is configured to display the elliptical marker over thelimbus.
 10. The system according to claim 1, wherein the images arefirst images, wherein the system further comprises a camera configuredto acquire multiple second images of the eye following the receipt, bythe controller, of the confirmation input, and wherein the controller isconfigured to treat the eye by performing an iterative process, eachiteration of the process including: verifying a position of a differentrespective one of the target regions in a most-recently acquired one ofthe second images, and in response to the verifying, firing a respectiveone of the treatment beams at the target region whose position wasverified during the iteration.
 11. The system according to claim 10,wherein the controller is configured to verify the position by verifyingthat a distance between an aiming beam and the target region whoseposition was verified during the iteration is less than a predefinedthreshold.
 12. The system according to claim 10, further comprising anillumination source, wherein the controller is further configured tocause the illumination source to intermittently flash visible light atthe eye such that the light illuminates the eye at least duringrespective acquisitions of the second images.
 13. The system accordingto claim 12, wherein a peak average intensity of the light over aduration of each of the flashes is between 0.003 and 3 mW/cm².
 14. Thesystem according to claim 12, wherein the controller is configured tocause the illumination source to flash the light at a frequency of atleast 60 Hz.
 15. The system according to claim 14, wherein the frequencyis at least 100 Hz.
 16. The system according to claim 10, furthercomprising an illumination source, wherein the controller is furtherconfigured to cause the illumination source to illuminate the eye withnear-infrared light at least during respective acquisitions of thesecond images.
 17. The system according to claim 16, wherein thecontroller is further configured to cause the illumination source tointermittently flash visible light at the eye while treating the eye.18. The system according to claim 1, further comprising an optical unitcomprising the radiation source and a plurality of beam emitters,wherein the controller is further configured to, prior to simulating theirradiation, cause the beam emitters to shine a plurality ofrange-finding beams on the eye, the range-finding beams being shaped todefine different respective portions of a predefined composite patternsuch that the predefined composite pattern is formed on the eye onlywhen the optical unit is at a predefined distance from the eye.
 19. Thesystem according to claim 18, wherein the range-finding beams are shapedto define two perpendicular shapes, and wherein the predefined compositepattern includes a cross.
 20. The system according to claim 1, furthercomprising an optical unit comprising the radiation source, wherein thecontroller is configured to cause the radiation source to irradiate thetarget regions while the optical unit is directed obliquely upwardtoward the eye and the eye gazes obliquely downward toward the opticalunit.
 21. The system according to claim 20, further comprising a wedge,wherein the optical unit is directed obliquely upward toward the eye byvirtue of being mounted on the wedge.
 22. The system according to claim1, wherein the controller is configured to simulate the irradiation bycausing the radiation source to irradiate the target regions withrespective aiming beams, which are visible in the images.
 23. The systemaccording to claim 22, wherein the controller is further configured to:superimpose a marker on each of the images, and prior to treating theeye, by processing the images, verify respective positions of the aimingbeams with respect to the marker, wherein the controller is configuredto treat the eye in response to verifying the positions of the aimingbeams.
 24. The system according to claim 23, wherein the controller isconfigured to verify the positions of the aiming beams by verifying thatthe aiming beams overlap the marker.
 25. The system according to claim23, wherein the controller is configured to verify the positions of theaiming beams by verifying that the aiming beams lie outside the marker.26. The system according to claim 23, wherein the controller isconfigured to treat the eye such that respective edges of the treatmentbeams impinge on respective portions of the eye over which the marker issuperimposed.
 27. The system according to claim 23, wherein the markeris elliptical.
 28. A system, comprising: a camera configured to acquirean image of an eye of a patient; a radiation source; and a controllerconfigured to: based on the image of the eye, identify a static regionin a field of view of the camera that includes a pupil of the eye, andtreat the eye by causing the radiation source to irradiate the eye withone or more treatment beams such that each of the treatment beamsimpinges on the eye outside the static region.
 29. The system accordingto claim 28, further comprising one or more beam-directing elements,wherein the controller is configured to treat the eye by aiming thebeam-directing elements at the target regions in sequence and firing thetreatment beams at the beam-directing elements, and wherein thecontroller is further configured to inhibit the beam-directing elementsfrom being aimed at the static region even while none of the treatmentbeams is being fired.
 30. The system according to claim 28, wherein thecontroller is configured to identify the static region by: receiving,from a user, a limbus-locating input indicating a location of the limbusin the image, and identifying the static region based on the location ofthe limbus.
 31. A method, comprising: displaying a live sequence ofimages of an eye of a patient; while displaying the sequence of images,simulating an irradiation of one or more target regions of the eye suchthat the simulated irradiation is visible in the images, by directingone or more beam-directing elements at the target regions in sequence;verifying the directing of the beam-directing elements by processing afeedback signal from an encoder for the beam-directing elements;subsequently to simulating the irradiation, receiving a confirmationinput from a user; and in response to receiving the confirmation inputand to verifying the directing of the beam-directing elements, treatingthe eye by irradiating the target regions of the eye with respectivetreatment beams.
 32. The method according to claim 31, whereinirradiating the eye with the treatment beams comprises irradiating theeye by firing the treatment beams at the beam-directing elements througha focusing lens, such that the beams are focused by the focusing lensprior to being directed, by the beam-directing elements, toward thetarget regions.
 33. The method according to claim 31, further comprisingsuperimposing, on each of the images, a marker passing through each ofthe target regions.
 34. The method according to claim 33, wherein themarker is elliptical.
 35. The method according to claim 31, wherein atleast part of each of the target regions is located within 1 mm of alimbus of the eye.
 36. The method according to claim 31, furthercomprising, prior to displaying the live images: displaying a stillimage of the eye; identifying an elliptical portion of the eye in thestill image, based on input from the user; and in response toidentifying the elliptical portion of the eye, superimposing anelliptical marker over the elliptical portion of the eye in each of theimages.
 37. The method according to claim 36, wherein superimposing theelliptical marker over the elliptical portion of the eye comprises:subsequently to identifying the elliptical portion of the eye,identifying an offset from a center of a limbus of the eye to a centerof the elliptical portion in the still image; and for each image of theimages: identifying the center of the limbus in the image; andsuperimposing the elliptical marker on the image such that the center ofthe elliptical marker is at the identified offset from the center of thelimbus.
 38. The method according to claim 36, wherein identifying theelliptical portion of the eye comprises: displaying, over the stillimage, (i) the elliptical marker, and (ii) a rectangle circumscribingthe elliptical marker; and subsequently to displaying the ellipticalmarker and the rectangle, in response to the user adjusting therectangle, adjusting the elliptical marker such that the ellipticalmarker remains circumscribed by the rectangle, until the ellipticalmarker is superimposed over the portion of the eye.
 39. The methodaccording to claim 38, further comprising identifying a limbus of theeye in the still image, wherein displaying the elliptical markercomprises displaying the elliptical marker over the limbus.
 40. Themethod according to claim 31, wherein the images are first images,wherein the method further comprising acquiring multiple second imagesof the eye following the receipt of the confirmation input, and whereintreating the eye comprises performing an iterative process, eachiteration of the process including: verifying a position of a differentrespective one of the target regions in a most-recently acquired one ofthe second images; and in response to the verifying, firing a respectiveone of the treatment beams at the target region whose position wasverified during the iteration.
 41. The method according to claim 40,wherein verifying the position comprises verifying that a distancebetween an aiming beam and the target region whose position was verifiedduring the iteration is less than a predefined threshold.
 42. The methodaccording to claim 40, further comprising intermittently flashingvisible light at the eye such that the light illuminates the eye atleast during respective acquisitions of the second images.
 43. Themethod according to claim 42, wherein flashing the light comprisesflashing the light such that a peak average intensity of the light overa duration of each of the flashes is between 0.003 and 3 mW/cm².
 44. Themethod according to claim 42, wherein flashing the light comprisesflashing the light at a frequency of at least 60 Hz.
 45. The methodaccording to claim 44, wherein the frequency is at least 100 Hz.
 46. Themethod according to claim 40, further comprising illuminating the eyewith near-infrared light at least during respective acquisitions of thesecond images.
 47. The method according to claim 46, further comprisingintermittently flashing visible light at the eye while treating the eye.48. The method according to claim 31, wherein treating the eye comprisestreating the eye using an optical unit, and wherein the method furthercomprises, prior to simulating the irradiation, shining a plurality ofrange-finding beams on the eye, the range-finding beams being shaped todefine different respective portions of a predefined composite patternsuch that the predefined composite pattern is formed on the eye onlywhen the optical unit is at a predefined distance from the eye.
 49. Themethod according to claim 48, wherein the range-finding beams are shapedto define two perpendicular shapes, and wherein the predefined compositepattern includes a cross.
 50. The method according to claim 31, whereinirradiating the target regions comprises irradiating the target regionsby firing the treatment beams from an optical unit directed obliquelyupward toward the eye while the eye gazes obliquely downward toward theoptical unit.
 51. The method according to claim 50, wherein the opticalunit is directed obliquely upward toward the eye by virtue of beingmounted on a wedge.
 52. The method according to claim 31, whereinsimulating the irradiation comprises simulating the irradiation bycausing the radiation source to irradiate the target regions withrespective aiming beams, which are visible in the images.
 53. The methodaccording to claim 52, further comprising: superimposing a marker oneach of the images; and prior to treating the eye, by processing theimages, verifying respective positions of the aiming beams with respectto the marker, wherein treating the eye comprises treating the eye inresponse to verifying the positions of the aiming beams.
 54. The methodaccording to claim 53, wherein verifying the positions of the aimingbeams comprises verifying that the aiming beams overlap the marker. 55.The method according to claim 53, wherein verifying the positions of theaiming beams comprises verifying that the aiming beams lie outside themarker.
 56. The method according to claim 53, wherein treating the eyecomprises treating the eye such that respective edges of the treatmentbeams impinge on respective portions of the eye over which the marker issuperimposed.
 57. The method according to claim 53, wherein the markeris elliptical.
 58. A method, comprising: based on an image of an eye ofa patient, which was acquired by a camera, identifying a static regionin a field of view of the camera that includes a pupil of the eye, andtreating the eye by causing a radiation source to irradiate the eye withone or more treatment beams such that each of the treatment beamsimpinges on the eye outside the static region.
 59. The method accordingto claim 58, wherein treating the eye comprises treating the eye byfiring the treatment beams at one or more beam-directing elements aimedat the target regions in sequence, and wherein the method furthercomprises inhibiting the beam-directing elements from being aimed at thestatic region even while none of the treatment beams is being fired. 60.The method according to claim 58, wherein identifying the static regioncomprises: receiving, from a user, a limbus-locating input indicating alocation of the limbus in the still image; and identifying the staticregion based on the location of the limbus.